[2] It may be triggered by bites from insects and arachnids such as spiders, fleas, or ticks, or from medications or surgery.

[1] Skin biopsy of the affected areas may show an increased number of eosinophils.

[2] Other conditions that may appear similar include cellulitis, contact dermatitis, and severe allergic reactions such as anaphylaxis.

[2] It may be triggered by bites from insects such as mosquitos,[5] spiders, fleas, or ticks, or from medications or surgery.

[3] As the condition tends to get better on its own taking steroids by mouth should generally only be tried if the rash covers a large area and it does not get better with other measures.